The invention relates to an apparatus for securing and clamping optical lenses requiring edge-machining, in particular spectacle lenses.
Where the term spectacle lenses is used below, it should be understood to mean optical lenses or lens blanks for spectacles made of the usual materials, such as polycarbonate, inorganic glass, CR-39, HI-Index etc., and with circumferential edges of any shape, which lenses or lens blanks may be, but do not have to be, machined on one or both optically effective surfaces prior to machining of the edge thereof.
In the field of spectacle lens edge-machining, the purpose of which is to finish the edge of a spectacle lens in such a way that the spectacle lens may be inserted into a spectacle frame, various arrangements or systems are known which serve to mount the spectacle lens for edge-machining and to clamp it between rotatable holding shafts of a spectacle lens edge-machining machine, which shafts are adjustable in the axial direction relative to one another.
These systems accordingly comprise at least the following components:
a securing or blocking member, which may be attached detachably to one side of the spectacle lens, (see for example EP-A-0 235 543: FIGS. 4 and 5; EP-A-0 839 603: FIGS. 1 and 2);
an adapter for the securing or blocking member, which may be connected rigidly to one of the holding shafts of the spectacle lens edge-machining machine and is constructed for rotation angle-oriented rotary drive of the securing or blocking member (see for example EP-A-0 235 543: FIGS. 1 to 3; EP-A-0 839 603: FIG. 5); and
a clamping assembly, which comprises a fastening portion, connectable rigidly to the other holding shaft of the spectacle lens edge-machining machine, and a clamping portion connected to the fastening portion, which clamping portion is constructed for force-locking engagement with the other side of the spectacle lens (see for example EP-A-0 995 546).
With respect to further known designs of the securing or blocking member and the adapter for the securing or blocking member reference is made to the leaflet xe2x80x9cWECO Block-up System. D 704. Wernicke and Co. GmbH, Dxc3xcsseldorf, Germany, March 1990xe2x80x9d and to document DE-A-198 31 305. Further, it is known in the prior art to attach the securing member to the optical lens by means of an adhesive film portion or pad which is adhesive on both sides (see for example DE-U-92 00 513). Finally, another known design of the clamping assembly is shown in document DE-A-25 06 866.
Taking as a basis the prior art according for example to EP-A-0 235 543, an object of the invention is to provide an apparatus for securing and clamping optical lenses, in particular spectacle lenses, which is improved with regard to handling relative to the previously known solutions and which is optimised also from the point of view of the rotary drive of the optical lens, which is as free from backlash as possible.
According to one aspect of the present invention, there is provided an apparatus for securing and clamping optical lenses requiring edge-machining, between first and second rotatable holding shafts, having
a securing member, which may be attached detachably to one side of the optical lens,
an adapter for the securing member, which may be connected rigidly to said first holding shaft and is constructed for rotation angle-oriented rotary drive of the securing member, and
a clamping assembly, which comprises a fastening portion connectable rigidly to said second holding shaft and a clamping portion connected to the fastening portion, which clamping portion is constructed for force-locking engagement with a second side of the optical lens,
wherein the clamping assembly has a spherical head with opposing sides and an axis of rotation, which spherical head is provided on each of its opposing sides with a projection having an end zone, and which spherical head is accommodated in a receiving portion with opposing sides and an axis of rotation, which receiving portion is provided on its opposing sides with channels or grooves extending parallel to the axis of rotation of the receiving portion, which channels each have a channel bottom and serve for substantially rotary play-free guidance of the projections, for which the channel bottom of each of the channels displays, in cross section, a shape complementary to the end zone of the associated projection, wherein the clamping portion may be swivelled relative to the fastening portion about a first tilt axis perpendicular to the axis of rotation of the spherical head and extending through the projections, and about a second tilt axis perpendicular to the axis of rotation of the spherical head and to the first tilt axis, while torque may be transmitted via the projections from the fastening portion to the clamping portion.
According to a second aspect of the present invention, there is provided an apparatus for securing and clamping optical lenses requiring edge-machining, between first and second rotatable holding shafts, having
a securing member, which may be attached detachably to one side of the optical lens,
an adapter for the securing member, which may be connected rigidly to said first holding shaft and is constructed for rotation angle-oriented rotary drive of the securing member, and
a clamping assembly, which comprises a fastening portion connectable rigidly to said second holding shaft and a clamping portion connected to the fastening portion, which clamping portion is constructed for force-locking engagement with a second other side of the optical lens, and
wherein the securing member and the securing member adapter each comprise rotary drive elements for form-fitting rotary drive of the securing member by the securing member adapter, and positioning elements for orientation with regard to angle of rotation of the securing member relative to the securing member adapter,
wherein the positioning elements on the securing member optionally on the securing member adapter take the form of a plurality of asymmetrically arranged projections with end faces, the end faces of which asymmetrically arranged projections lie in a common plane perpendicular to the axis of rotation, while the positioning elements on the securing member adapter optionally on the securing member take the form of recesses associated in complementary manner with the asymmetrically arranged projections, said recesses starting from a flat surface perpendicular to the axis of rotation, and
wherein the axial distance between the rotary drive elements and the positioning elements on the securing member is different from an axial distance between the rotary drive elements and the positioning elements on the securing member adapter, such that, if the securing member is moved axially towards the securing member adapter and rotation angle orientation has not yet been achieved, first of all the projections come to rest against the flat surface and then, once rotation angle orientation is complete, the projections enter into the recesses, whereupon the rotary drive elements come into engagement with one another.
According to a third aspect of the present invention, there is provided an apparatus for securing and clamping optical lenses requiring edge-machining, between first and second rotatable holding shafts, having
a securing member, which may be attached detachably to one side of the optical lens,
an adapter for the securing member, which may be connected rigidly to said first holding shaft and is constructed for rotation angle-oriented rotary drive of the securing member, and
a clamping assembly, which comprises a fastening portion connectable rigidly to said second holding shaft and a clamping portion connected to the fastening portion, which clamping portion is constructed for force-locking engagement with a second side of the optical lens,
wherein the securing member is attachable to the optical lens by means of an adhesive film portion having first and second sides with adhesive on both of said first and second sides of the adhesive film portion, which exhibits greater adhesive power on said first side thereof that faces the securing member than on said second side thereof that faces the optical lens.
Constructing the clamping assembly according to the invention allows very precise, backlash-free torque transmission together with very smooth angle adjustment. The spherical head mounted in the receiving portion thereof and having two projections allows movements superimposed in the manner of a cardan joint about two tilt axes with virtually backlash-free rotary drive by the associated holding shaft due to the engagement between the projections and the channels in the receiving portion. Since the channel bottom of each of the channels displays, in cross section, a shape complementary and dimensionally matching, respectively, to the end zone of the associated projection, form-fitting engagement is obtained between the projections and the channels when viewed with the channel in cross section and the pin in longitudinal section, which form-fitting engagement is advantageous for backlash-free rotary motion transmission between spherical head and receiving portion. The backlash-free torque transmission thus obtained with low wear and at the same time very smooth angle adjustment is an essential prerequisite for a highly precise edging of spectacle lenses with machinery suitable for industrial production.
Precisely aligned orientation relative to the first tilt axis of the two projections of the spherical head may be achieved by the introduction of a pin, protruding on both sides beyond the spherical head so as to form projections, into a through-hole which extends with its central axis through the centre of the sphere and encloses the pin in play-free manner.
By means of the cylindrical surface zones on the two projections, interacting with flat guide surfaces of the channels associated with these surface zones, it is ensured that, in the event of swivel movements about the second tilt axis, the substantially rotary play-free guidance of the projections in the channels is maintained.
In view of a smooth angle adjustment of the clamping portion it is further of advantage if the end zones of the projections provided on the spherical head take the form of a spherical cap.
A construction of the pin which is favourable from the point of view of manufacture provides, that the pin is of continuously cylindrical construction, with the exception of its spherical cap-shaped end zones, such that the above-mentioned cylindrical surface zones are fixed in their corresponding diameters by the pin diameter itself, which is identical thereto. The overall length of the pin may be fixed by the radial spacing of the channel bottoms, which is greater only by slight movement play than the pin length measured externally over the spherical cap-shaped ends of the pin.
The pin may be enclosed by the through-hole in the spherical head by interference fit, but it is preferably accommodated in the through-hole by sliding fit and this provides the advantage that, upon insertion of the pin into the through-hole, it does not have to be ensured that the axial projection dimensions correspond exactly and with low tolerance. Upon insertion of the spherical head into the receiving portion, the pin, which is axially displaceable in the through-hole of the spherical head, adjusts itself, as it were, automatically to the correct axial projection dimensions in accordance with the position of the channel bottoms.
Axial securing of the spherical head after its introduction into the receiving portion may be by means of a two-part retaining ring engaging behind the spherical head.
The spherical head may be associated with the fastening portion of the clamping assembly, while the receiving portion may be associated with the clamping portion of the clamping assembly. Detachable fastening of the clamping assembly to the relevant holding shaft may proceed by means of a locking means on the fastening portion. Rotary drive by this holding shaft can be effected, by a channel formed in the end of the fastening portion, in which channel a cross-pin borne by the holding shaft engages non-rotatably and without play.
The clamping portion can comprise a covering for force-locking engagement with the optical lens, which covering consists of a material which is comparatively softer than the lens, to prevent damage to the lens surface during lens loading, edge-machining and lens removal.
Continuing the concept behind the invention, the arrangement for securing optical lenses comprises a securing member and a securing member adapter, which, are especially constructed on the one hand for form-fitting rotary drive of the securing member by the securing member adapter and on the other hand for positioning, correct with regard to angle of rotation, of securing member and securing member adapter. To this end, both securing member and securing member adapter comprise on the one hand rotary drive elements and on the other hand positioning elements. The positioning elements take the form of a plurality of projections on one of the two components consisting of securing member and securing member adapter and of recesses complementary to the projections on the other of the two components. The arrangement is such that the end faces of the projections lie in a common imaginary plane perpendicular to the axis of rotation, while the recesses start from a flat surface plane-parallel to this common plane. Moreover, the axial distance between the rotary drive elements and the positioning elements on the securing member is different from the axial distance between these elements on the securing member adapter. Owing to this construction, when the securing member approaches the securing member adapter, which is thus not yet at the correct angle of rotation, first of all the end faces of the projections come to rest against the flat surface comprising the recesses, without the rotary drive elements as yet engaging with one another. If correct orientation with regard to angle of rotation is then achieved by rotating the securing member relative to the securing member adapter, wherein the end faces of the projections slide on the above-mentioned flat surface, the projections finally enter the recesses for fixing the relative position with regard to angle of rotation, provided that securing member and securing member adapter are axially aligned, until, as the securing member further approaches the securing member adapter, the rotary drive elements move into engagement with one another.
Three projections and consequently three recesses may be provided, wherein the projections or the end faces thereof and the recesses or the inlet openings thereof each form the corners of matching triangles. Due to this configuration, the securing member comes to lie in secure, tilt-free manner on the securing member adapter, without the rotary drive elements yet entering partially into undesired engagement. The projections hold the securing member at a distance from the securing member adapter until the correct relative position with regard to angle of rotation is reached. Then all the rotary drive elements move extensively into engagement.
To simplify insertion of the projections into the recesses, provision is made for the projections to comprise bezels or bevels starting from their end faces and/or the recesses to comprise bezels or bevels at their inlet openings starting from the flat surface.
Preferably, the projections are located on the securing member adapter and the recesses on the securing member.
According to another important aspect of the invention, the securing member may comprise a hub portion comprising the positioning elements and an outer annular portion connected resiliently therewith, which bears the rotary drive elements of the securing member. The resilient connection between the annular portion and the hub portion allows simplified, improved adaptation of the securing member to the convexity of the lens to be machined.
The above-mentioned resilient connection between hub portion and annular portion may be achieved by a plurality of webs or the like distributed evenly about the circumference. During injection-molding of the securing member from a suitable thermoplastic material, hub portion, webs and annular portions may be molded in one piece. Instead of individual webs, a circumferentially continuous, annular, thin-walled connection may also be provided between hub portion and annular portion, which connection allows similar flexible deformation between annular portion and hub portion for the purpose of adaptation to lens convexity.
The rotary drive elements on the securing member and on the securing member adapter are constructed, as complementary annular toothing or annular toothed portions. This annular toothing has the effect of centring a securing member and securing member adapter due to the radial tooth orientation thereof optionally together with a complementary conical construction of the annular toothing.
An especially-constructed adhesive film portion may be provided, with which the securing member and the optical lens may be connected together detachably but non-rotatably for the edge-machining operation. The two adhesive layers of the adhesive film portion, which is adhesive on both sides, exhibit different adhesive powers, such that the adhesive power on the side of the adhesive film portion facing the securing member is greater than on the lens side. In this way, when the lens is removed it is ensured that the adhesive film portion remains stuck detachably to the securing member and thus does not have to be removed from the lens surface, which could cause superficial damage to the lens or leave adhesive residues on the lens. To ensure easier removability of the adhesive film portion from the securing member, a tab projecting beyond the outer circumference of the securing member may be provided on the adhesive film portion, which tab is non-adhesive at least on its side facing the optical lens, in order to prevent adhesion to the lens.
The adhesive film portion of the arrangement may be extraordinarily thin in comparison to the prior art. For example, it has a thickness of between only approximately 0.025 and 0.2 mm, compared to a conventional thickness of approximately 0.5 to 0.8 mm. Due to this very small thickness, which is made possible due to the resilient deformability of the securing member as described, no deformation or flexing phenomena occur in the adhesive film portion due to the torsional forces at work.